Shaded pole single phase induction motor ppt, presentation Description
Since this shaded portion is short circuited, the current is produced in it in such a direction to oppose the main flux. The current carried by stator winding produces alternating flux. Construction is simple and robust because there is no centrifugal switch. The coils are made up of copper and it is highly inductive in nature.
Let us discuss the constructional details, partnervermittlung hilden diagrams and working of shaded pole motors in detail. The flux produced by this induced emf has no effect on the main flux and hence distribution of flux remains uniform and the magnetic axis lies at the center of the pole. The poles are divided into two unequal halves.
The torque-speed characteristic is same as that of a three-phase one, having both starting and also running torque. Advantages and Disadvantages of Shaded Pole Motor The advantages of shaded pole induction motor are Very economical and reliable. The poles of shaded pole induction motor consist of slots, which are cut across the laminations. Rotor The rotor of shaded pole induction motors is Squirrel Cage type rotor. Since starting torque, efficiency and power factor are very low, these motors are only suitable for low power applications e.
The rotor bars are provided with a degree skew. The phasor diagram of two currents in both cases, and the torque-speed characteristics with two windings having different values of capacitors. According to Lenz law the direction of this current is so as to oppose the cause producing it the decreasing alternating current.
So the magnetic axis lies along the middle of the unshaded part. When the flux remains almost constant at its maximum value. Thus, as the flux increases in each field pole, there is a concentration afflux in the main segment of each pole, while the shaded segment opposes the main field flux.
When the flux decreases from maximum positive value to zero. The stator has two winding one is main winding and another is auxiliary winding Auxiliary winding with a high resistance in series is to be added along with the main winding in the stator. The rotor is of the squirrel-cage type and is under the influence of this moving field. Since the copper band is short circuit the current starts flowing in the copper band due to this induced emf.
Small C-frame shaded-pole squirrel-cage motor. The speed reversal is also difficult and expensive as it requires another set of copper rings. The stator is provided with two simple coils, which can be directly connected to the mains. This is to obtain an optimum starting torque and for limiting the torque dip during run-up.
Rotating field of a Shaded Pole Motor Synchronous Motors Synchronous ac motors are constant-speed electric motors and they operate in synchronism with line frequency. This loop is known as the shading coil. The short-circuited copper coil described above is placed in this slot. The slot is approximately one-third distance from the edge of the pole. So we can call this part as the shaded part and other parts of the pole as unshaded part.
Shaded Pole Single Phase Induction Motors The stator of the shaded pole single phase induction motor has salient or projected poles. As soon as this torque starts to revolve the rotor, additional torque is produced by single-phase induction-motor action.
Working of Shaded Pole Induction Motor The operation of the motor can be understood by referring to figure which shows one pole of the motor with a shading coil. The direction of rotation is from the unshaded side to the shaded ring side of the pole. The direction of rotation is from the unshaded side to the shaded ring. This increases the strength of main flux in the shaded part.
This change of flux induces emf in the shaded coil. The rotor consists of a cylindrical permanent two-pole magnet, which is diametrically magnetized.
When a single phase supply is given to the stator of shaded pole induction motor an alternating flux is produced. Split Phase Induction Motor In addition to the main winding or running winding, the stator of single phase induction motor carries another winding called auxiliary winding or starting winding. Thus shaded coils aids in producing the rotating flux and thus the single phase Induction motor is converted into self starting one using the Shading coil. The current in the shading coil is out of phase with the current in the main field winding.
So the shading ring does not affect the distribution of main flux. So, only the forward rotating field is present, and the no backward rotating field exists. Advantages and Applications No centrifugal switch is needed.
Now let us discuss why the axis shift occurs when current is passed through the winding and how the shading coil aids in producing the shift. When the flux remains almost constant at its maximum value- In this region the rate of rise of current and hence flux remains almost constant. This coil is known as shading coil. So the flux in the shading coil decreases and it opposes the main flux. When the alternating current through the coil increases, it induces a current in the shading coil.
The current in this coil delay the phase of magnetic flux in that part of the pole in order to provide a rotating magnetic field. In order to produce rotating magnetic field there must be some phase difference.
Thus, rotating magnetic field is produced in such motor, giving rise to starting torque. Now let us consider that an alternating current is passed through the excited winding which surrounds the pole. The direction of current in shading coil is such as to oppose the cause producing it from Lenz law. Hence the flux mostly crowds or shifts towards the unshaded part of the pole. This shifting flux is like a rotating weak field moving in the direction from the unshaded portion to the shaded portion of the pole.
The second one is to be rated for continuous duty, as it is used for running. It finds applications in fans and blowers in heaters and air conditioners.
Shaded pole motor diagram and construction explained
When the flux decreases, the current reverses in the shaded coil to maintain the flux in the same direction. So the flux in shading coil opposes the decrease in main flux and strengthens it. The smaller portion carries the copper band and is called as shaded portion of the pole. The function of the centrifugal switch has been described earlier.
Shaded-pole Induction Motor
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